Taylor Swift has accused Gigi Hadid of the "ultimate betrayal" according to reports.

The Blank Space singer and the 20-year-old model have built up a firm friendship, with Gigi starring in Taylor's Bad Blood video. But tensions have reportedly arisen between the pair since rumours of a romance between Gigi and Taylor's ex Joe Jonas began to surface in the last few weeks.

"Things have been tense with Taylor and Gigi since she started hanging out with Joe," a source told British magazine Closer. "Gigi's really fallen for him but Taylor's branded their reported romance as the 'ultimate betrayal'."

Taylor, 25, dated Joe back in 2008 before being dumped by him over the phone. Meanwhile Gigi has recently split from singer Cody Simpson and has been seen cuddling up to Joe on a number of occasions. While Joe's representative claimed the pair were just friends, they were spotted this week kissing and hugging on an LA street.

"Gigi has begged Taylor not to cut her off from her inner circle and insists Joe is sorry for the way he treated her all those years ago," the source continued. "They've spoken about it but Taylor feels uncomfortable about the whole thing - she spends lots of time with Gigi and doesn't want to see Joe all the time."

Joe, 25, recently claimed that he and Taylor were now friends after burying the hatchet. But the insider adds that Taylor, who is now dating DJ Calvin Harris, hasn't actually forgiven him for his past behaviour.

"She's happy with Calvin but it's always a sore point when Joe is mentioned," they added. "She doesn't want to have a fall out with Gigi but obviously it's a far from ideal situation."